Biomedical Engineering Reference
In-Depth Information
Kang et al. (2007) report that the activity of the enzyme glucose oxides (GO
x
) can be easily
affected by temperature, humidity, and toxic chemicals (
Wilson and Turner, 1992
). Thus, the
enzymeless glucose sensor is an attractive alternative. Kang et al. (2007) point out that
recently CNTs and transition metallic nanoparticles (NPs) have been used in biosensors.
Owing to their high surface/volume ratio CNTs are attractive materials for electroanalysis
(
Merkoci et al., 2005; Zhao and Ju, 2006
). Kang et al. (2007) have developed an effective
nonenzymatic glucose sensor by using catalytic oxidation to electrode-post the copper
nanoclusters onto the electrode modified with Nafion (Nf)-solubilized CNTs. They used this
sensor to analyze glucose in real blood serum samples.
A single-fractal analysis is adequate to describe the binding and the dissociation kinetics in
Figure 7.1a
. The values of (a) the binding rate coefficient,
k
, and the fractal dimension,
D
f
,
for the binding phase for a single-fractal analysis, and (b) the dissociation rate coefficient,
k
d
, and the fractal dimension,
D
fd
, for a single-fractal analysis are given in
Table 7.1
. The
affinity,
K
,(
¼
k
/
k
d
) value is 86.48. This is the first run in the sequence.
A single-fractal analysis is also adequate to describe the binding and the dissociation kinetics
for the chronological runs b and c. In this case, the affinity,
K
, values are 64 and 74.73,
respectively. For these three chronological runs depicted and analyzed in
Figure 7.1a-c
, the
average affinity,
K
, value is 75.07.
Figure 7.2a
shows the increase in the binding rate coefficient,
k
, with an increase in the frac-
tal dimension,
D
f
, for a single-fractal analysis. For the data shown in
Figure 7.2a
, the binding
rate coefficient,
k
, is given by:
D
0
:
8872
5
10
15
k
¼ð
0
:
32
0
Þ
ð
7
:
4a
Þ
f
Only three data points are available. Two of the points are exactly identical. The fit is good.
The availability of more data points would lead to a more reliable fit. The binding rate coef-
ficient,
k
, exhibits less than first (equal to 0.8872) order of dependence on the fractal dimen-
sion,
D
f
, or the degree of heterogeneity on the biosensor surface.
Table 7.1: Binding and dissociation rate coefficients and affinity values, and fractal dimensions
for the binding and the dissociation phase using cyclic voltametry (CV) for 1 mM glucose
in solution to Nf(nafion)-CNTs (carbon nanotube)-GCE (glass carbon electrode)
(Kang et al., 2007).
Run
Number
k
k
d
k/k
d
D
f
D
fd
D
f
/D
fd
1.0 10
16
1
0.32 0
0.0037 0.0002
86.48
0.6650 0.0518 1.503
1.0 10
16
2
0.32 0
0.05 0.0
64
1.0
1
10
15
3
0.2989
0.305
0.004
0.0
74.73
0.926
0.0428
1.0
3.6
0.926
Repeat runs under the same conditions in chronological sequence 1, 2 and 3.
